अथ तां रजनीं तत्र कृतार्थौ रामलक्ष्मणौ।
ऊषतुर्मुदितौ वीरौ प्रहृष्टेनान्तरात्मना॥
atha tāṁ rajanīṁ tatra kṛtārthau rāma-lakṣmaṇau
ūṣatur muditau vīrau prahṛṣṭenāntar-ātmanā
atha tām rajanīm = that night; tatra = there at Siddhāśrama; kṛtārthau = were successful in carrying out the purposes of Viśvāmitra; rāma-lakṣmaṇau = Rāma and Lakṣmaṇa; ūṣatuḥ = They resided; muditau = delighted; vīrau = the heroes; prahṛṣṭena = and so were happy; antar-ātmanā = in their minds.
The heroes Rāma and Lakṣmaṇa were successful in carrying out the purposes of Viśvāmitra, delighted and so were happy in Their minds. They resided there at Siddhāśrama that night.
1 This is his attempt to serve Lord Rāma; this is not his attempt to bless Him with the association of His natural potency, the goddess of fortune, for Viśvāmitra is always aware of his subordinate position in relation to the Supreme Lord Rāma. He is aware that Rāma acts like his disciple and student to teach the world how to behave as a disciple and a student.
Now that Viśvāmitra was successful in his mission [of bringing Lord Rāma to guard his sacrifice], he now departed for Mithilā on [some] pretext to unite Lord Rāma with the goddess of fortune who had incarnated as the daughter of King Janaka.1 This is described in this chapter.